Middleware

Middleware in JustSaying is an extensibility feature that provides a way to add your own code around handlers to add things like custom logging, exactly once handling, or de-duplication.

Configuration

Defaults

There are two middlewares that are always added to the message handling pipeline: HandlerInvocationMiddleware and StopwatchMiddleware.

The handler invocation middleware is always the innermost middleware in a pipeline, and is responsible for resolving a handler and calling it.

The stopwatch middleware wraps the handler invocation one, and ensures that the IMessageMonitor.HandlerExecutionTime method is called correctly.

These defaults cannot currently be removed, but you can add additional middleware around them.

Adding additional middleware

Middleware pipelines are configured on a per-subscription basis, using the SqsReadConfiguration.WithMiddlewareConfiguration API:

c.WithReadConfiguration(rc =>
    rc.WithMiddlewareConfiguration(m =>
    {
        m.Use<MyMiddleware>();
        m.UseExactlyOnce<SimpleMessage>("simple-message-lock");
    }))

This will produce the following pipeline, where before/after refer to when code executes before or after the call to the next middleware.

Before - MyMiddleware Before - ExactlyOnceMiddleware Before - StopwatchMiddleware Before - HandlerInvocationMiddleware After - HandlerInvocationMiddleware After - StopwatchMiddleware After - ExactlyOnceMiddleware After - MyMiddleware